Production of stencil sheets for use in duplicating



Patented Mar. 4, 1930 PATENT OFFICE ARMAND DI; WAELE, OF LONDON, ENGLAND, ASSIGNOR TO D. GESTE'INER, LIMITED, OF LONDON, ENGLAND iPRODUC'I ON OF STENCIL SHEETS FOR USE IN DUPLICATING No Drawing. Application filed May 3, 1928, Serial No. 274,975, and in, Great Britain July 22, 1927.

This invention relates to stencil sheets for use in duplicating manuscript or typewritten matter, drawings and thelike of the kind in which the ink-resisting medium of the stencil sheet is adapted to be displayed 'or its character altered by the local application of pressure to the stencil sheet with the aid of a style or by type faces.

In the production of such stencil sheets,

compositions containing gelatinizing organiccolloids which dissolve orsolate in organic liquids but not in water are in certain cases employed as the ink-resisting medium of the stencil sheet which usually consists of'a sheet of highly porous material, normally yoshino paper, coated or impregnated with such composition, which may for instanceinclude nitrocellulose andv an oily'material, for instance castor oil, as a softening or tempering agent. Where the gelatinizing organic colloid is of the character indicated it has hitherto been necessary to employ volatile organic liquids in considerable proportion relatively to the colloid in order to obtain products which are sufiiciently mobile to be applied to sheets of highly porous material, such as yoslnno paper, for the purpose of coating or impregnating them or otherwise to be used inobtam: ing sufficiently attenuated layers or films of such compositions.

The use of large proportions of orgamc liquids is open to objections of a more or less serious character, owing, for instance, to the losses due to evaporationif the vapours are allowed to escape or to the cost of the necessary recovery plant if such losses are to be avoided.

Moreover, with most of the solvents avallable the fire riskis considerable and there may also be a risk of injury to the health of the workers unless precautions are taken to prevent the vapours being inhaled.

The object of the present invention is to provide an improved process of produclng stencil sheets with the aid of compositlons containing gelatinizing organic collo ds which dissolve or solate in organic liquids but not in water.

The invention is based on the-observation 50 that these gelatinizing organic compounds when in the form of relatively weak gels or viscous sols may be converted into emulsions in aqueous media and that the emulsions thus obtained may be employedin forming the film or coating of ink-resisting medium of stencil sheets. I

The invention may therefore be stated to consist in the employment in the production of the composition adapted to constitute the ink-resisting medium of a stencil sheet of gelatinizing organic colloids which do not dissolve in water, peptized or converted into weak gels or viscous sols with the aid of organic liquids, in the form of emulsions in aqueous media.

The gelatinized organic colloids employe'l in the production of the ink-resisting medium of stencil sheets are normally softened, weakened or tempered by the addition of suitable agents. Thus, for example, when cellulose esters are used as the gelatizing organic colloid oily bodies or mixtures of oily bodies are usually associated therewith.

In accordance with the present invention such tempering or softening agents may be employed in the formation of the weak gels or sols which are dispersed in aqueous media for the purpose of obtaining compositions adapted to be applied, for instance, to sheets of highly porous material. 4

\Vhen in accordance with the invention a cellulose ester is used as the sole or main gelatini'zing constituent of the ink-resisting medium of the stencil sheet the cellulose ester is peptized or converted into a sol of high viscosity or a relatively weak gel bythe employment of suitable organic liquids and the sol or gel is emulsified in an aqueous medium.

Thus, for example, in accordance with the invention nitrocellulose of a relatively low degree of nitration together with castor oil in the presence or absence of otherbodies adapted to modify the properties of the nitro-- cellulose may be converted into a gel or viscous sol and the resulting gel or viscous sol emulsified in an aqueous medium.

Conveniently the aqueous medium contains a gelatinizing organic colloid which solates in water, a protein such as a carbohydrate col- In converting the gel'atiniz'ing organic colloid which is not normally dispersible in water into a gel or sol of high viscosity theemployment of a volatile organic solvent may be necessary or desirable and it may be convenient to use a relatively considerable proportion of suchsolvent, a proportion'of which may be evaporated prior to forming the aqueous dispersion.

In order to indicate in greater detail the nature of the invention the following particulars are given by way of example of a method of producing'a dispersion of nitro-cellulose in an aqueous medium.

Collodion cotton is moistened with amyl acetate and castor oil is added, the proportion of amyl ace'zate' used being sufiicient to enable an apparently homogeneous jelly-like composition to be formed.

If necessary or desirable organic solvents which are more volatile than amyl acetate may be used and such solvents, including the amyl acetate, may be evaporated or allowed to evaporate from the composition and leave a stiff jelly-like mass. The nitrocellulose and castor oil may be present in the composition in the ratio of 1 of theformer to between 5 and 7 of the latter. The precise proportions will depend, as is well known, on the character of the nitrocellulose used and to some extent also on the purity of the castor oil.

The jelly-like mass thus obtained is then emulsified with an aqueous dispersion of gelatine or agar, the proportion of gelatine or agar relative .to the nitrocellulose being ll of the former to 10 of the latter.

For facilitating the emulsification, sulphonated sperm oil may be used and in the composition a proportion of ricinoleic acid or of.

vantage as this material would appear to as sist in stabilizing the emulsion.

While sulphonated sperm oil has been referred to above as the emulsifying agent, a

variety of other materials which are adapted 1 to-facilitate the emulsification of oily mate rials in water may be used; for instance when ricinoleic acid or a similar fatty acid is cone tained in the composition the addition of a proportion of ammonia will facilitate emulsification in consequence apparently of the formation of ammonium soaps of ricinoleic acid. I I

Alternatively ammonium soaps previously formed may be added to the other ingredients.

It is to be understood that the invention is not to be regarded as limited in its scope in View of the detailed description above given as the invention extends to the production of stencil sheets in which one of the gela-tinizing constituents or the main orsole gelatinizing constituent of the ink-resisting medium of the stencil sheet is a material which is not soluble or normally dispersable in water by the employment of compositions containing such an organic colloid gelated or converted into a gel or viscous sol which gel or sol is emulsified in an aqueous medium and to the stencil sheet so produced.

Having now described by invention, what I claim as new and desire to secure by Letters Patent is 1. Stencil sheets having a coating composition or ink-resisting medium the main gelatinized constituent of which is a gelatinized cellulose ester in intimate association with a gelatinized organic colloid dispersible in water. i

2. The process of producing stencil sheets adapted to be stencilized bypress'ure which comprises solating a cellulose ester in an organic liquid emulsifying the resulting sol in an aqueous medium and coating a highly porous sheet material with the emulsion thus obtained.

/ 3. The process of producing stencil sheets adapted to be stencilized by pressure which comprises converting nitrocellulose of a relatively low degree of nitration together with an oily tempering agent and a volatile solvent into a viscous'sol and emulsifying the resulting viscous sol in an aqueous medium.

4. The process of producing stencil sheets adapted to be stencilized by pressure which comprises solating nitrocellulose in the presence of castor oil and a volatile organic solvent to form a viscous sol and emulsifying the viscous sol with a dispersion of a protein in an aqueous medium.

In testimony whereof I have signed my name to this specification. 

